Key-operating arrangement for short-wave tube transmitters



Dec.23, 1930. w. MOSER ET AL 1,786,257

KEY OPERATING ARPANGEMENT FOR SHORT WAVE TUBE TRANSIITTERS Filed Aug. 18, 1925 Fly. 1 Z I /12 W n Hg. 2 15 12 m ll I V um/aims WILHELM MOSER Patented Dec. 23, 1930 UNITED STATES WILHELM MOSER AND ERICH TOD, OF'BEitLIN, ennnenyhnss onons 'IO GESELL- SCI-IAFT F'U'B DRAHTLOSE TELEGRAIHI IPORATION OF GERMANY B; H., orv BERLIN, GERMANY, A COR- KEY-OPERATING ARRANGEMENT non smsawavmees 'TnansMIrrERs Application filed August 18, 1925, Serial It'd 1,002, aiiiriii Geeuany se temter 4, 1924.]

Our invention relates, broadly, to tube transmitters for transmitting communications by means of radio frequency electromagnetic Waves, and, more particularly, to a keying arrangement especially adapted for use with very short wave lengths.

An object of the invention is to provide an arrangement of the above kind that will be simple in constructionand operation, one which will permit the key to be placed at any desired distance from the transmitting tube and one which will not cause sparking at the key contacts.

Other objects will be apparent from the following description and claims when considered with the accompanying drawing, in which Fig. 1 represents atube transmitter with one embodiment of our invention applied thereto, and

Fig. 2 represents a tubetransmitter with another embodiment of our invention applied thereto.

An arrangement isknown fordetuningkeying which comprises two different oscillation circuits coordinated to a generator tube,

which are alternately rendered operative in performing the key work. This arrangee ment will always be used to advantage, if, in such detuning key-work, a considerable difference in wave length is to be obtained Now, when Working with very short wave lengths, it has been found that successful telegraphic operation is feasible even at extremely small change in wave length. Indeed, a change of the fraction of 1 1000, is practicable for keying purposes. There are various means adapted to produce wave variations of such small degree. For instance, the oscillation circuit of the transmitter tube can be detuned by varying either the self-inductance or the capacitance in the rhythm of the key signals. The changes in self-inductance, for instance, can be obtained by shortcircuiting a turn or spiral of the coil, or a *of the inductance. V 7

Now, according tothe present invention, an ohmicresistance'is inserted in a direct c urrent circuit: of the transmitter tube, and the 12.5. :key in parallelto the'same. The said ohmic resistance could bearranged, for example, in :the' direct current" anode lead The resista-nce being-either short circuited or left in circuit, the same becomes causative of a small variation of the anodedirect currentpotenitial ,iand consequently of the generated wavelength. The advantage which this scheme 'otlersover the d'etuning method of keying happens iflth'e capacity: be changechinstead previously mentionedtresides in that the key" 7 is inserted in a=direct current, lead, so that it can be arranged at any desired'distance from :thetransmitte'ru y f :lMore; appropriate than the arrangement of. the resistance in the anode lead isthe dis 1 --position 'of the same in the direct current grid dead, since'zthe currents flowing therein are very small. This arrangement ofl'ers the adwant'age that the energies to be keyed become :of'very-low value, with the consequence that ,sparkin'g is wholly-wprecluded.

-,-5Referring to Fig; 10f. the drawing, 1 denotes a usual type of three-element electron :discharge tube comprising a heated filamentary cathode, a cold plate anode and a cold grid shaped- ."contr'ol electrode, all sealed Withiiian evacuated envelope. This tube has its circuits connected to generate sustained oscillations. In the particular embodiment shown, the oscillation circuit 2 comprising capacitance 10 and inductance 11 connected in parallel determine the generated wave length. i

This circuit is connected to the anode of i, tube 1 thru a blocking condenser 12 and to the control electrode thru a grid condenser 3. The cathode of tube 1 is connected to an appropriate point on inductance 11 by the adjustable lead 13.

Across the'grid condenser 3 is a grid leak 4 to determine the amount of negative potential which the rid shall accumulate during operation. Also connected across thegrid condenser 3 is a key 5 connected thru twochoke coils 6 for keeping high frequency from the key 5.

Anode current is supplied by source 14 acting thru inductance coil 15.

It will be easily seen that, when key 5 is depressed, the grid leak 4 and grid condenser 3 will be short-circuited, permitting the bias 011 the grid to change, this causing the generated wave length to change.

In Fig. 2 the same reference characters refer to the same parts as in Fig. 1. The tube 1 is connected to generate sustained oscillations. However, in this case, instead of varying the direct current flowing from the grid, the direct current flowing in the anode circuit is varied by keying. This will also cause the generated wave length to change, as pointed out above.

Having described our invention, we are entitled to all modifications thereof as fall fairly within its spirit and scope as defined by the following claims:

1. In combination, a three-element electron discharge tube having a control electrode condenser to enable the control electrode to accumulate a bias; a leak across said condenser; means comprising a tuned circuit connected to the anode and control electrode of the tube for causing said tube to produce oscillations; and means for short-circuiting said leak consisting solely of a key and a pair of choke coils.

2. In combination, a three element electron discharge tube; means for causing said tube to produce oscillations including a tuned circuit connected across the anode and the control electrode of said tube; said tuned circuit comprising an inductance and capacitance; a control electrode condenser interposed between said circuit and said control electrode; a leak across said condenser, means for short-circuiting said leak consisting solely of a key and a pair of choke coils, and a lead from the cathode of said tube to a point on said inductance.

WILHELM MOSER. DR. ERICH TOD. 

